In radiotherapy using heavy ions, tumors are bombarded with accelerated particles. A particle accelerator forms and emits a particle beam, typically a proton beam from a proton beam nozzle. During the treatment, the proton beam must be accurately directed at the tumor. Depending on the position of the tumor in the body, different irradiation positions (fields) are provided for the patient. One system for positioning patients during radiotherapy is provided for in U.S. patent application Ser. No. 12/208,807 filed on Sep. 11, 2008, having U.S. Publication No. 2009-0070936, entitled “Patient Positioner System.”
While that system provides for significantly improved positioning of the patient within the room in which the radiotherapy by providing different angles as well as an increased positioning envelope, the actual angle at which the proton beam is emitted and directed toward the patient may need to be adjusted. For instance, it may be desirable to allow a patient to lie on his or her back and administer the proton beam in a horizontal direction. However, in another treatment session, it may be desirable to again low the patient to lay on his or her back but to administer the proton beam along an axis that is oblique to the horizontal plane, such as by an angle of about sixty degrees. The different angles may be desired depending on the location of the tumor and the best path to avoid damaging cells that are not part of the tumor.
As such, while being able to adjust the position of the patient is desirable, it is also desirable to adjust the position of the proton beam nozzle and therefore the axis along which the proton beam is administered.
In the past, very large scale structures were used to mount and position the proton beam nozzle. These structures would require very large buildings and rooms for performing the radiotherapy. The present invention relates to improvements in radiotherapy systems and particularly positioning of proton beams in radiotherapy systems.